One of the greatest parts of becoming an extension agent is learning a wealth of new information on a wide array of subjects. Often, this information comes from going to training classes held by University of Georgia specialists, but sometimes we stumble onto information that we can’t look away from while we should be doing other things. This is going to be about the latter.
Last week I had a client mention El Niño and La Niña and the confusion that those terms create. I had to confess, while I have understood those terms, and what each meant for our weather, I couldn’t recall the details instantly on the phone. This led me down a path that eventually included logging onto a Southeast climate webinar that also included a “2023 Southeast Year in Review.”
First, let’s review the El Niño and La Niña climate patterns that we’re all expected to remember. El Niño and La Niña are known as ENSO (El Niño Southern Oscillation), and they influence our winter weather here in the Southeastern U.S. Normally, tradewinds blow warm surface waters west off the coast of South America toward Asia. This encourages a moderate upwelling of deeper, cooler water on our Pacific Coast. La Niña is an extreme of this event, and the winds are stronger than normal, pushing more warm water west and creating more upwelling of deeper, cooler water on our Pacific Coast. This cool water causes the pacific jet stream to shift northward, and typically creates drier winter conditions for the Southeast. This is known as La Niña.
When the warmer surface water doesn’t get blown westward toward Asia, and no upwelling of deeper, cooler water occurs, the warm water on our Pacific Coast causes a southward shift of the Pacific jet stream. This typically creates wetter winter conditions in the Southeastern U.S. This is known as El Niño.
We are currently in an El Niño pattern, but according to the NIDIS Southeast Climate Webinar the prediction is that we should be transitioning to ENSO neutral (normal) conditions as we progress through spring. Now I know what you’re thinking. We’ve been in a drought. Aren’t we supposed to have had more moisture during El Niño? Yes, but many of the effects were late this year and it’s a regional prediction. As it turns out, parts of South Carolina and Middle Georgia have been getting plenty of rain and, overall, the Southeast was near average for precipitation for 2023.
The year 2023 was the fifth warmest year for the U.S. on record (129 years), and the Southeast had our second warmest year on record in that same period. Trends like this may explain why the U.S. Department of Agriculture (USDA) changed our plant hardiness zone last November. I was reminded of this a few weeks ago (by a rather cynical neighbor) when the morning temperature at my house was five degrees. USDA has updated the Plant Hardiness Zone Map (PHZM) used by an estimated 80 million gardeners as a tool to determine which plants are appropriate for the climate of a given location.
The map is based on the average of the lowest annual winter temperatures. The year 2012 was the last update of the map prior to 2023 and according to the USDA press release, “about half the country shifted to the next warmer half zone.” This includes most of our area. Previously most of Northwest Georgia was listed as 7b, with an average extreme minimum temperature of 5-10 degrees Fahrenheit, while the new map has us listed as 8a, with an average extreme minimum temperature of 10-15 degrees.
The USDA website https://planthardiness.ars.usda.gov provides more details on how to properly use the PHZM, how it was created, searchable maps and printable versions. This change of our hardiness zone doesn’t mean that we should start re-landscaping our yards, or shopping for plants that are at the limit of our new zone. Homeowners should assume that we will continue to get our share of extreme low temperatures as we did in mid-January, and when we do, our most cynical neighbors will say, “I told you so.”
If you have any questions related to our new zone and how it affects your landscape, give us a call.
Shane Kornberg is the agriculture and natural resource agent for University of Georgia Extension, Whitfield County. Contact him at Kornberg@uga.edu or call the Whitfield County Extension office at (706) 278-8207.